Method for inspecting electrode surface quality

ABSTRACT

The invention relates to a method for inspecting the surface quality of the deposit created on the surface of an electrode in the electrolytic treatment of metals. According to the invention, a cathode ( 1 ) obtained from electrolytic treatment is illuminated by at least one light source ( 3 ) placed in an oblique position with respect to the plane ( 12 ) that constitutes the cathode surface, and an image of the illuminated surface ( 12 ) is made with at least one camera ( 8 ); said image is then transmitted to an image processing arrangement ( 9 ), and on the basis of said image, there are defined possible irregularities of the surface in order to classify the deposit ( 11 ) located on the cathode for the next processing step.

FIELD OF THE INVENTION

The present invention relates to a method for inspecting the surfacequality of the deposit created on the surface of an electrode in theelectrolytic treatment of metals by means of an image made of theelectrode surface.

BACKGROUND OF THE INVENTION

In the electrolytic treatment of metals, the desired metal isprecipitated on the surface of the electrode, i.e. cathode, used in theelectrolytic treatment. The treatment is performed by means of electriccurrent in a tank designed for electrolytic treatment; in said tank,there is provided liquid, i.e. electrolyte, and in said electrolytethere is partially immersed a number of plate-like anodes and plate-likecathodes in an alternating fashion and made electro conductive material.The desired metal is precipitated onto the cathode either so that in theelectrolytic treatment, there is used a soluble anode made of the samemetal as the one to be precipitated, like in the precipitation ofcopper, or so that in the electrolytic treatment, there is used aninsoluble anode, like in the precipitation of zinc or nickel, and thatthe metal to be precipitated is dissolved in the electrolyte used in theelectrolytic treatment and is precipitated directly from the electrolyteonto the cathode.

In connection with the precipitation process carried out in theelectrolytic treatment of metals, the electrolyte usually contains smallamounts of impurities that are obtained either from the electrolyteitself or from the metal to be precipitated; said impurities tend to beprecipitated onto the cathode along with the rest of the deposit.Moreover, the electrolyte may contain gas bubbles that affect theformation of the deposit. Moreover, the electric current density in theelectrolytic treatment may fluctuate, in which case the precipitation ofmetal onto the cathode varies at different spots of the cathode surface.Impurities, gas bubbles and fluctuations in the current density causeirregularities, i.e. nodules, on the cathode surface, and said nodulesaffect the classification of the cathode for further treatment. Thedetection of nodules on the cathode surface by visual inspection isdifficult and slow, particularly as there are hundreds of cathodes beingprocessed daily in the production plants of the current scale.

SUMMARY OF THE INVENTION

The object of the present invention is to eliminate drawbacks of theprior art and to achieve a method for inspecting the electrode surfacequality on the basis of an image made of the electrode surface. Theessential novel features of the invention are apparent from the appendedclaims.

According to the invention, in a tank designed for electrolytictreatment, there is provided liquid, i.e. electrolyte, for conductingthe electric current; in said liquid, there are at least partly immersedplate-like anodes and cathodes made of an electro conductive materialand arranged in an alternating fashion, in order to precipitate thedesired metal onto electrode serving as the cathode. In the end of theprecipitation process, the cathode complete with the deposit is liftedout of the tank, whereafter the cathode is subjected to an inspectionprocess according to the invention in order to classify said cathode onthe basis of the cathode surface quality. The cathode surface qualityinspection according to the invention is advantageously carried outprior to stripping the deposit from the cathode mother plate, inconnection with the transportation from the electrolytic tank to thestripping station. In order to inspect the cathode surface quality, inthe immediate vicinity of the cathode conveyor track, there is providedat least one checkpoint where the cathode surface is illuminated with atleast one light source from a direction that is oblique with respect tothe cathode conveyor track, in which case the irregularities of thecathode surface cast shadows on said surface. In the checkpoint, therealso is installed at least one camera that makes an image from theilluminated cathode surface or monitors the illuminated surface in anessentially continuous fashion. The image obtained of the cathodesurface is further transmitted to an image processing device where theimage is processed by measuring physical qualities of the shadows castby the irregularities. On the basis of the physical qualities of theshadows, the cathode is classified in a desired fashion.

In a preferred embodiment of the invention, the inspection of thequality of a cathode surface is carried out while conveying cathodes ina transversal conveyor that is connected to the operation of acyclically operated stripping station and is thus itself cyclicallyoperated. In a cyclically operated transversal conveyor, the cathodemovement is stopped during the stripping of the deposit that takes placein the stripping station. Thus the inspection according to the inventionis advantageously carried out in one inspection station for one cathodeat a time. When necessary, the cathode can also be inspected in severalinspection stations.

For the cathode surface quality inspection according to the invention,in the inspection station there is installed at least one light source,so that the beams generated by the light source are directed to thesurface of the cathode to be inspected at an oblique angle, the size ofsaid angle varying within the range 0-90 degrees, advantageously 30-60degrees. Now the possible irregularities of the surface cast shadows onthe cathode surface, and the length and area of said shadows aredirectly proportional to the length and area of the irregularity inquestion. In order to define the surface quality of the illuminatedcathode, the inspection station also includes at least one camera thatis advantageously installed in an essentially perpendicular positionwith respect to the cathode surface under inspection; by means of saidcamera, there is obtained an image of the illuminated surface that mayinclude shadows caused by possible irregularities. When desired, thecamera can also be installed in a spot and at an angle that deviate fromthe essentially perpendicular position in relation to the surface of thecathode under inspection, but so that the shadows caused byirregularities on the cathode plate surface can still be an object formaking an image. The image is transmitted from the inspection station toan image processing device, where the length and area of the shadowscontained in the image are measured, and for instance the number andlocation of the shadows is defined. On the basis of the results obtainedin the inspection, the deposits to be stripped from the cathode motherplate in the stripping station are classified in various classes forfurther processing.

In the cathode surface inspection according to the invention, there isadvantageously used one light source for each surface to be illuminated.Thus the shadows cast by possible irregularities are made essentiallysharp-edged and hence essentially easily definable, because the lightcausing the shadow comes from one direction only, and beams coming fromseveral different light sources do not intersect. It is, however,possible that in the inspection according to the invention there areused at least two light sources for each illuminated surface, but thistype of arrangement is advantageous essentially in cases where theirregularities as such are sharp-edged.

A light source meant for the illumination of the surface to be inspectedis installed, with respect to the surface to be illuminated, so that thelight source is located outside the area that is formed by the normalsof the plane that constitutes the cathode surface. Thus the light sourceis placed at an oblique angle with respect to the normal of the planethat constitutes the surface to be illuminated, and the size of saidangle is within the range 0-90 degrees, advantageously 30-60 degreeswhen measured at the spot where the beams coming from the light sourcemeet the central line of the plane defined to be in the inspectionstation. In position and location, said plane defined to be in theinspection station essentially corresponds to the plane formed by thecathode to be illuminated. By adjusting the angle of the light sourcewith respect to the normal of the plane that constitutes the surface tobe illuminated towards a sharper angle, the length of the shadows castby possible irregularities can be extended, in which case the dimensionsof the irregularities can be defined in and advantageously more accuratefashion. The employed light source can be for instance a halogenfloodlight, a fluorescent tube or an incandescent lamp. When necessary,in front of the light source, there can be arranged radiant field stopsthat guide the proceeding of the beams onto the surface to beilluminated.

In the method according to the invention, the image of the illuminatedcathode surface is advantageously shot by one camera per each surface tobe illuminated. When desired, the number of said cameras can be two ormore, in which case the dimensions of the shadows cast by possibleirregularities can be defined as the average of two or more images. Whenusing two or more cameras, the positioning of said cameras can be usedto particularly affect possible special dimensions to be defined on thebasis of the obtained image, which special dimensions should be definedin connection with the inspection. While using two or more cameras, thecameras can be chosen so that they represent different types, in whichcase for instance one camera is a video camera, and the other is aphotographic camera. On the other hand the angle where the beams comingfrom the light sources meet the central point of the plane thatconstitutes the cathode surface is maintained the same.

The camera that shoots a picture of the illuminated cathode surface isinstalled, with respect to the surface of the cathode to be inspected,so that the camera is located in an essentially perpendicular positionwith respect to the plane that constitutes the cathode surface. Thecamera is installed so that the image obtained in the camera is sharp atleast in one spot of the cathode surface. Advantageously the camera isinstalled so that it is located in an essentially central position inthe area where the cathode under inspection is stopped by the conveyingoperation for performing the inspection. When using two or more cameras,the cameras are positioned, mutually and with respect to the plane to bemonitored, advantageously in an essentially symmetrical fashion.

In the method according to the invention, the image made of the cathodesurface under inspection is further transmitted to an image processingdevice; in said device, there is installed a computer program thatcalculates for instance the number, size and primary location of shadowsand thus the number, size and primary location of correspondingirregularities contained on the cathode surface. The measurement resultsare recorded in a microprocessor included in the image processingdevice, and the obtained results are used for classifying the depositlocated on the cathode. By means of the calculated values and therecorded history, the deposit to be stripped from the cathode isclassified according to the further processing steps that are mostreasonable for the deposit in question. On the basis of the recordedhistory information, possible changes in the electrolytic process canalso be detected, because for instance changes in the location ofirregularities are usually caused by changes in the conditions of theelectrolytic process itself.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail with reference to the appendeddrawings, where

FIG. 1 represents a preferred embodiment of the invention when seen as aschematical illustration from behind the camera used in said embodiment,

FIG. 2 illustrates a preferred embodiment according to FIG. 1, when seenin the direction A—A, and

FIG. 3 illustrates a preferred embodiment illustrated in FIG. 1, whenseen in the direction B—B.

DETAILED DESCRIPTION OF THE INVENTION

According to FIG. 1, 2 or 3, the cathode 1 is conveyed to an inspectionstation and supported by support means 2 during the inspection of thesurface of the deposit 11 located on the cathode. For the inspection,beams 4 of light are directed to the surface of the cathode 1 from alight source 3. The light source 3 is installed outside the area formedby the normals 5 of the plane 12 that constitutes the cathode surface,so that the beams 4 that reach the surface of the cathode 1 form anangle of 45 degrees with the centre line 6 of the plane that constitutesthe cathode surface. Shadows 7 that are created by the beams 4 and castby possible irregularities located on the surface of the cathode 1 aremonitored by a camera 8, which is connected to an image processingdevice 9 and to a microprocessor 10 connected thereto, in order toclassify the deposit 11 located on the surface of the cathode 1advantageously for further processing.

Moreover, FIG. 3 illustrates how the surfaces of the deposits 11 locatedon both sides of the mother plate of the cathode 1 can be inspected inone and the same inspection station by placing a light source 3 and acamera 8 on both sides of the cathode 1.

What is claimed is:
 1. A method for inspecting surface quality of adeposit created on a surface of an electrode in electrolytic treatmentof metals, comprising illuminating essentially all the surface of acathode obtained from electrolytic treatment by at least one lightsource placed in an oblique position with respect to a plane thatconstitutes the cathode surface, making an image of the illuminatedsurface with at least one camera, transmitting said image to an imageprocessing arrangement, and on the basis of said image, definingpossible irregularities of the surface in order to classify the depositlocated on the cathode for a next processing step.
 2. A method accordingto claim 1, wherein the light source illuminating the cathode surface isplaced at an angle of 0-90 degrees, when measured at the spot where thebeams coming from the light source meet a central line of the plane thatconstitutes the cathode surface.
 3. A method according to claim 2,wherein the angle is between 30 and 60 degrees.
 4. A method according toclaim 1, wherein the light source illuminating the surface of thecathode is installed, with respect to the plane constituting the cathodesurface, so that the light source is located outside an area formed bynormals of the plane that constitutes the surface of the cathode.
 5. Amethod according to claim 1, wherein in order to make an image of theilluminated surface, the camera is installed in an essentiallyperpendicular position with respect to the plane that constitutes thesurface of the cathode under inspection.
 6. A method according to claim1, wherein in order to make an image of the illuminated surface, thecamera is installed essentially in the centre of the plane thatconstitutes the surface of the cathode under inspection.
 7. A methodaccording to claim 1, wherein in order to make several images of theilluminated surface, cameras are installed essentially on the centreline of the plane that constitutes the surface of the cathode underinspection.
 8. A method according to claim 1, wherein in order toclassify the cathode on the basis of an image made by the camera, insaid image there are defined shadows cast by the irregularities locatedon the surface of said cathode.
 9. A method according to claim 1,wherein the images obtained from the surfaces of separate cathodes arerecorded in a microprocessor provided in connection with an imageprocessing device.
 10. A method according to claim 9, wherein historyinformation recorded in the microprocessor is utilised in adjustment ofthe electrolytic process.
 11. A method according to claim 1, wherein theemployed light source is a halogen floodlight.
 12. A method according toclaim 1, wherein the employed light source is a fluorescent tube.
 13. Amethod according to claim 1, wherein the employed light source is anincandescent lamp.
 14. A method according to claim 1, wherein theemployed camera is a photographic camera.
 15. A method according toclaim 1, wherein the employed camera is a video camera.